Question

Difficulty: MediumCryptographic Concepts and Algorithms

A security administrator is updating the enterprise baseline controls for data protection across various infrastructure layers. Match each cryptographic mechanism on the left with its primary operational security function on the right.

  • Elliptic Curve Diffie-Hellman Ephemeral (ECDHE)Perform dynamic key exchange to establish asymmetric ephemeral session keys that provide perfect forward secrecy.
  • Hash-based Message Authentication Code (HMAC)Combine a symmetric key with a cryptographic hash function to verify data integrity and message authenticity.
  • Password-Based Key Derivation Function 2 (PBKDF2)Derive cryptographic keys from user passwords using iterative computational delay to mitigate offline brute-force attacks.
  • ChaCha20-Poly1305Provide authenticated bulk data encryption optimized for low-power mobile or embedded hardware.

Answer

ECDHE pairs with establishing ephemeral keys for perfect forward secrecy; HMAC pairs with combining a secret key and hash for message authentication and integrity; PBKDF2 pairs with key stretching user passwords to resist offline brute-force attacks; ChaCha20-Poly1305 pairs with low-overhead authenticated bulk encryption for constrained hardware.
Elliptic Curve Diffie-Hellman Ephemeral (ECDHE) provides perfect forward secrecy by generating temporary session keys. Hash-based Message Authentication Code (HMAC) verifies message integrity and source authenticity by combining a secret key with a hash function. Password-Based Key Derivation Function 2 (PBKDF2) performs key stretching by hashing passwords over thousands of iterations to slow offline cracking. ChaCha20-Poly1305 is a high-speed AEAD stream cipher optimized for mobile and embedded devices.

Step-by-Step Solution

1
Analyze ECDHE capabilities
Identify that ephemeral key exchange mechanisms guarantee perfect forward secrecy during transport layer negotiations.
Temporary keys ensure compromise of long-term keys does not decrypt past sessions.
2
Analyze HMAC capabilities
Identify that combining secret key material with hashing yields authentication and integrity verification.
Standard cryptographic hashes provide integrity, but adding a secret key (HMAC) adds sender authenticity.
3
Analyze PBKDF2 capabilities
Identify that password-based key derivation functions implement key stretching.
Repeated iteration adds artificial computation time, making brute-force cracking prohibitively slow.
4
Analyze ChaCha20-Poly1305 capabilities
Identify stream cipher AEAD suitable for resource-constrained platforms.
ChaCha20 is designed to run efficiently in software on systems lacking hardware AES acceleration.

Key Concept

Cryptographic Primitives and Functional Applications
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